| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a glass substrate for HDD which inhibits head crushing of an outer peripheral end portion and contributes to an enlargement of a recording area even in a case of a magnetic recording medium for HDD with a high surface recording density. <P>SOLUTION: A glass substrate 50 for HDD is used for producing a magnetic recording medium for HDD with the surface recording density of 630 Gb/sq.in. or more. When A represents an amount of deviation in the height of the outer peripheral end portion of the glass substrate 50 from a reference plane that is defined on a principal surface 51 of the glass substrate 50, a circumferential variation X of A calculated according to an expression (1) is 3% or less and circumferential TIR (Total Indicated Runout) of the outer peripheral end portion of the glass substrate 50 is 0.4μm or less. The expression (1): variation X(%)=ä(MAX-MIN)/(MAX+MIN)}×100 (in the expression (1), MAX represents a circumferential maximum value of A and MIN represents a circumferential minimum value of A). <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
